The MIJ A2000's from the 80-and mid 2000's had a better leather quality. The internals of these gloves were the best at the time, but compared to now the internals that were in the MIJ gloves are comparable to a mid level glove.
the MIV A2000's currently have a slightly thinner leather but the colors are truer and last much longer. The internals are top notch.
Current MIJ A2000's are a selective run that have better leather quality and with the newer internals.
Like anything its a preference thing.